Look for the Mariners to hold off confirming their deal with outfielder Alex Jackson, their first-round pick, probably until early next week.

The news broke Wednesday that an agreement was in place that included a $4.2 million signing bonus.

But there was no official confirmation, although parties on both sides privately acknowledge an agreement on terms is in place. That absence of immediate confirmation is neither surprising nor unusual.

Clubs routinely decline to confirm such agreements until the player passes a physical examination to avoid possible legal entanglements if that exam reveals something unforeseen.

The normal procedure for all clubs on major deals, such as this one, is to bring the player into town for an examination by the club’s own physicians.

Typically, that also provides the club with a public-relations bonus by calling a news conference to announce the deal. Jackson, once signed, is expected to be be assigned to the Peoria in the Arizona Rookie League.

Clutchiness

Start with a disclaimer: Measuring clutch performance is one of the tougher stat metrics in baseball — in part because it’s tough to define a clutch situation.

But…third baseman Kyle Seager ranks second among all players, to Detroit first baseman Miguel Cabrera, in terms of driving in runs over the standardized average.

The formula computes a number from the number of runners on base for a batter, the number of runs driven in and measures it against that standardized average for those situations.

Cabrera is plus-19.9, followed by Seager at plus-15.8.

Miami’s Casey McGehee is third at plus-14.8, followed by Angels outfielder Mike Trout at plus-13.7, Arizona’s Paul Goldschmidt at plus-13.5 and Robinson Cano at plus-13.1

Now the negatives: Outfielder Michael Saunders ranks as the eighth-worst at minus-13.0, and outfielder Stefen Romero is 27th-worst at minus-11.5.

Rehab plans

Triple-A Tacoma is about to get a further infusion of big-league talent.

Tentative plans call for outfielder Michael Saunders to begin his rehab assignment Friday for the Rainiers, while first baseman/outfielder Corey Hart will start Saturday.

Both will join first baseman Justin Smoak, who began his assignment Wednesday by going 0-for-3 with a walk in a 4-2 victory over Colorado Springs. Smoak is recovering from a strained left quadriceps muscle.

Saunders is battling a sore right shoulder that surfaced June 6 on a swing at Tampa Bay. Hart is recovering from a strained left hamstring that occurred while running the bases May 18 at Minnesota.

While Smoak and Saunders are expected to make quick returns to active duty, Hart is likely to require most, if not all, of the permissible 20 days.

The Mariners activated outfielder Julio Morban, 22, from extended spring training and assigned him to the Double-A Jackson roster.

Morban played six games in April at Tacoma, and went 5-for-20, before returning to extended spring to continue his recovery from a broken right leg suffered suffered last Aug. 21 while playing for Jackson.

Baseball America ranked Morban as the organization’s No. 11 prospect prior to the season. He batted .295 last season at Jackson with seven homers and 44 RBIs in 86 games prior to his injury.

Short hops

The Mariners have gone 36 games without allowing an unearned run. … Outfielder James Jones showed no day-after effects from getting hit in the helmet Wednesday on a throw while trying to beat out a swinging bunt. Jones remained in Wednesday’s game. He went 1-for-4 in Thursday’s loss. … The Mariners had won eight straight day games before Thursday’s loss. … Robinson Cano’s 20-game road hitting streak is the longest current such streak in the majors.

Looking back

It was 24 years ago Friday — June 20, 1990 — that Ken Griffey Jr. hit an inside-the-park homer that lifted the Mariners to a 3-2 victory over the Royals in Kansas City.

It was 2-2 when Griffey hit a two-out line drive up the left-field line in the fifth inning against Kevin Appier. The ball got away from left fielder Jim Eisenreich, and Griffey circled the bases.

On tap

The Mariners open a three-game weekend series against the Royals at 5:10 p.m. (PDT) Friday in Kansas City. Right-hander Hisashi Iwakuma (5-3 and 2.59 ERA) will face Royals right-hander James Shields (8-3 and 3.50).

Root Sports will carry the game.

The series against the Royals continues with 11:10 a.m. (PDT) games Saturday and Sunday before the Mariners return to Safeco Field for a six-game homestand against Boston and Cleveland.